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MCQs in Modulation Part XIII

Compiled MCQs in Modulation Part 13 of the series as one topic in Electronic System and Technologies (Communications Engineering) in the ECE Board Exam.

This is the Multiples Choice Questions Part 13 of the Series in Modulation as one of the Communications Engineering topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies, Communications Books, Journals and other Communications References.

Online Questions and Answers Topic Outline

MCQs in Amplitude Modulation

MCQs in Phase Modulation

MCQs in Sound Pressure Level

MCQs in Frequency Modulation

MCQs in Pulse Modulation

MCQs in Modulation Series

Following is the list of multiple choice questions in this brand new series:

Continue Practice Exam Test Questions Part XIII of the Series

601. It is the first stage of the receiver and is therefore often called the receiver front end.

a. mixer

b. RF section

c. local oscillator

d. IF stage

602. One of the following cannot be used to remove the unwanted sideband in SSB. This is the

a. filter system

b. phase-shift method

c. third method

d. balanced modulator

603. R3E modulation is sometimes used to

a. allow the receiver to have a frequency synthesizer

b. simplify the frequency stability problem in reception

c. reduce the power that must be transmitted

d. reduce the bandwidth required for transmission

604. To provide two or more voice circuits with the same carrier, it is necessary to use

a. ISB

b. carrier reinsertion

c. SSB with pilot carrier

d. Lincomplex

605. A type of AGC is similar to conventional AGC except that the receive signal is monitored closer to the front end of the receiver and the correction voltage is fed forward to the IF amplifiers

a. ISB

b. delayed AGC

c. complex AGC

d. simple AGC

606. Having an information signal change some characteristics of a carrier signal is called

a. multiplexing

b. modulation

c. duplexing

d. linear mixing

607. A circuit that compensates for minor variations in the received RF signal level

a. automatic volume control

b. automatic frequency control

c. automatic gain control

d. automatic phase control

608. Which of the following is not true about AM?

a. the carrier amplitude varies

b. the carrier frequency remains constant

c. the carrier frequency changes

d. the information signal amplitude changes the carrier amplitude

609. A modulator circuit performs what mathematical operation on its two inputs?

a. addition

b. multiplication

c. division

d. square root

610. If m is greater than 1, what happens?

a. normal operation

b. carrier drops to 0

c. information signal is distorted

d. nothing happens

611. The outline of the peaks of a carrier has the shape of modulating signal and is called _______.

a. trace

b. wave shape

c. envelope

d. carrier variation

612. Overmodulation occurs when

a. Vm > Vc

b. Vm < Vc

c. Vm = Vc

d. Vm = Vc = 0

613. The new signal produced by modulation are called __________.

a. spurious emission

b. harmonics

c. intermodulation products

d. sidebands

614. An AM signal has a carrier power of 5W, the percentage of modulation is 80 percent. The total power sideband is _________.

a. 0.8 W

b. 1.6 W

c. 2.5 W

d. 4.0 W

615. For 100 percent modulation, what percentage of power is in each sideband

a. 25 percent

b. 33.3 percent

c. 50 percent

` d. 100 percent

616. An AM transmitter has a percentage of modulation of 88, the carrier power is 440 W. The power in one sideband is

a. 85 W

b. 110 W

c. 170 W

d. 610 W

617. An AM signal without the carrier is called ______.

a. SSB

b. vestigial sidebands

c. FM signal

d. DSB

618. It is a form of amplitude modulation in which the carrier is transmitted at full power, but only one of the sidebands is transmitted.

a. SSBFC

b. SSBSC

c. SSBRC

d. ISB

619. With single-sideband full carrier, 100% modulation would mean a carrier power of how many percent of the total transmitted power?

a. 80%

b. 20%

c. 50%

d. 40%

620. It is a form of amplitude modulation in which the carrier is suppressed and one of the sidebands removed

a. SSBFC

b. ISB

c. vestigial sideband

d. SSBSC

621. It is a form of amplitude modulation in which one sideband is totally removed and the carrier voltage is reduced to approximately 10% of its unmodulated amplitude

a. independent sideband

b. SSBFC

c. SSBRC

d. SSBSC

622. It is a form of amplitude modulation in which a single carrier frequency is independently modulated by two different modulating signal.

a. vestigial sideband

b. DSBFC

c. independent sideband

d. SSBFC

623. It is a form of amplitude modulation in which the carrier and one complete sideband are transmitted, but only part of the second sideband is transmitted.

a. independent sideband

b. vestigial sideband

c. DSBFC

d. SSBSC

624. It is the rms power developed at the crest of the modulation envelope of SSBSC.

a. carrier power

b. total transmitted power

c. sideband power

d. peak envelope power

625. Which of the following is not true about single-sideband transmission?

a. power is conserved

b. selective fading is eliminated

c. bandwidth is conserved

d. tuning is easy

626.A circuit that produces a double sideband suppressed carrier signal is called ____________.

a. filter

b. mixer

c. demodulator

d. balanced modulator

627. A balanced modulator is sometimes called _________.

a. balanced ring modulator

b. balanced resistor modulator

c. balanced lattice modulator

d. any of these

628. A type of filter that receives electrical energy, converts it to mechanical vibrations and then converts the vibrations back to electrical energy at its output.

a. crystal filter

b. mechanical filter

c. LC filter

d. SAW filter

629. A type of filter that uses acoustic energy rather than electromechanical energy to provide excellent performance for precise bandpass filtering.

a. SAW filter

b. RC filter

c. mechanical filter

d. crystal filter

630. The difference between the IF and the BFO frequencies is called _________.

a. information signal

b. beat frequency

c. carrier signal

d. heterodyned signal

631. It is a circuit which is a narrowband PLL that tracks the pilot carrier in the composite SSBRC receiver signal and uses the recovered carrier to regenerate coherent local oscillator frequencies in the synthesizer.

a. beat frequency oscillator

b. mechanical filter

c. local oscillator

d. carrier recovery circuit

632. A system that provides narrowband voice communications for land mobile services with nearly the quality achieved with FM systems and do it using less than one-third the bandwidth.

a. SSBSC

b. DSBFC

c. ACSSB

d. SSBAC

633. It is a process of combining transmissions from more than one source and transmitting them over a common facility such as metallic or optical fiber cable or a radio-frequency channel.

a. buffering

b. modulation

c. multiplexing

d. demultiplexing

634. It is an analog method of combining two or more analog sources that originally occupied the same frequency band in such a manner that the channels do not interfere with each other.

a. ATM

b. FDM

c. TDM

d. WDM

635. It is a multiplexing method that uses double-sideband suppressed-carrier transmission to combine two information sources into a single composite waveform.

a. QM

b. WDM

c. TDM

d. FDM

636. Single-sideband transmitters are rated in _________.

a. rms power

b. dc power

c. average power

d. peak envelope power

637. In an SSB transmitter, one is most likely to find a __________.

a. class C audio amplifier

b. tuned modulator

c. class B RF amplifier

d. class A RF output amplifier

638. Indicate in which one of the following only one sideband is transmitted:

a. H3E

b. A3E

c. B8E

d. C3F

639. One of the following cannot be used to remove the unwanted sideband in SSB. This is the

a. filter system

b. phase-shift method

c. third method

d. balanced modulator

640. R3E modulation is sometimes used to

a. allow the receiver to have a frequency synthesizer

b. simplify the frequency stability problem in reception

c. reduce the power that must be transmitted

d. reduce the bandwidth required for transmission

641. To provide two or more voice circuits with the same carrier, it is necessary to use

a. ISB

b. carrier reinsertion

c. SSB with pilot carrier

d. Lincomplex

642. The main advantage of SSB over standard AM or DSB is

a. less spectrum is used

b. simpler equipment is used

c. less power is consumed

d. a higher modulation percentage

643. In SSB, which sideband is the best to use?

a. upper

b. lower

c. neither

d. depends upon the use

644. The output of an SSB transmitter with a 3.85 MHz carrier and a 1.5 kHz sine wave modulating tone is

a. a 3.8485 MHz sine wave

b. a 3.85 MHz sine wave

c. 3.85, 3.8485 and 3.8515 MHz sine waves

d. 3848.5 and 3851.5 MHz sine waves

645. An SSB transmitter produces a 400 V peak to peak signal across a 52 ohm antenna load. The PEP output is

a. 192.2 W

b. 384.5 W

c. 769.2 W

d. 3077 W

646. The output power of SSB transmitter is usually expressed is terms of

a. average power

b. RMS power

c. peak to peak power

d. peak envelope power

647. An SSB transmitter has a PEP rating of 1 kilowatts. The average output power is in the range of

a. 150 to 450 W

b. 100 to 300 W

c. 250 to 333 W

d. 3 to 4 kW

648. In amplitude modulation technique, the unmodulated carrier is referred to as having___..

a. 100% modulation

b. 0% modulation

c. 50% modulation

d. overmodulated

649. What is the process in radio communication where the information or intelligent signal is at lower frequency is put unto higher radio frequency for transmission to receiving station?

a. detection

b. mixing

c. modulation

d. demodulation

650. Which of the following signals is suppressed by balanced modulator circuit?